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NAME
v.db.update - Allows to update a column in the attribute table connected to a vector map.
KEYWORDS
vector, database, attribute table
SYNOPSIS
v.db.update
v.db.update help
v.db.update map=string [layer=integer] column=string [value=string] [qcolumn=string] [where=string] [--verbose] [--quiet]
Parameters:
- map=string
- Vector map to edit the attribute table for
- layer=integer
- Layer to which the table to be changed is connected
- Default: 1
- column=string
- Column to update
- value=string
- Value to update the column with (varchar values have to be in single quotes, e.g. 'grass')
- qcolumn=string
- Column to query
- where=string
- WHERE conditions for update, without 'where' keyword (e.g. cat=1 or col1/col2>1)
DESCRIPTION
v.db.update allows to assign a new value to a column in the
attribute table connected to a given map. Alternatively, values can
be copied from another column in the table.
NOTES
v.db.update is just a front-end to db.execute to allow easier usage.
For complex SQL UPDATE statements, db.execute should be used.
EXAMPLES
Spearfish: adding new column, inserting selectively a specified value:
g.copy vect=fields,myfields
v.db.addcol myfields col="polynum integer"
v.db.update myfields col=polynum val=42 where="label='V. White#1'"
v.db.select myfields
Spearfish: adding new column, copying values from other table column with
on the fly calculation:
g.copy vect=fields,myfields
v.db.addcol myfields col="polynum integer"
v.db.update myfields col=polynum qcol="cat*2"
v.db.select myfields
Type cast (type conversion) of strings to double precision (unsupported by DBF driver):
v.db.update mygeodetic_pts col=zval qcol="CAST(z_value AS double precision)" \
where="z_value <> 'N/A'"
SEE ALSO
db.execute,
v.db.addcol,
v.db.addtable,
v.db.connect,
v.db.droptable,
v.db.join,
v.db.select
GRASS SQL interface
AUTHOR
Moritz Lennert (mlennert@club.worldonline.be)
Last changed: $Date: 2007-06-29 00:51:12 -0700 (Fri, 29 Jun 2007) $
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